Move Comes Amid Tougher Competition from Rivals in Cable Industry

AT&T Inc. expanded its planned rollout of high-speed Internet service to as many as 100 cities and towns, amid tougher competition as rivals in the cable industry bulk up.

The telecom giant said Monday it will now target major metropolitan areas including Chicago, Los Angeles and San Francisco. The bulk of the new locations overlap with service areas for Comcast Corp. and Time Warner Cable, which have agreed to merge in a $45...